Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, and the like. These wireless networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the Universal Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). Examples of multiple-access network formats include Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA) networks.
A wireless communication network may include a number of base stations or “node Bs” that can support communication for a number of user equipments (UEs). A UE may communicate with a base station via downlink and uplink. The downlink (or forward link) refers to the communication link from the base station to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the base station.
A base station may transmit data and control information on the downlink to a UE and/or may receive data and control information on the uplink from the UE. Packets that a UE desires to transmit are queued up at the UE, and the base station makes decisions regarding when the UE should be scheduled for uplink transmission and how many resources to assign it.
Thus, mobile (e.g., cellular) telephones have traditionally communicated over a network of specialized base stations. Most current mobile telephones connect to a cellular network of base stations, which may in turn be interconnected to the public switched telephone network (PSTN). In some cases, where data packets are supported by the wireless communication protocol, the cellular network of base stations may be communicatively coupled (e.g., via one or more gateway devices) with a data packet network, such as the Internet, thereby enabling UEs (e.g., mobile telephones) to browse the web and/or perform other data packet transactions (e.g., receive and/or transmit data packets) with other devices, such as computer servers. The base stations (or “cellular towers”) generally provide coverage over large areas. The area coverage of such a tower is sometimes referred to as a macrocell. These base stations are typically positioned to bring the greatest coverage to the greatest number of cellular telephone users. The above-described traditional cellular telephone network is referred to herein as a “mobile core network” (or simply “mobile core”).
Thus, cellular networks such as those described above are referred to herein as a “mobile core network” (or simply “mobile core”). It should be appreciated that, although terms typically associated with particular network standards and protocols have been used in describing exemplary mobile core networks above, mobile core networks as discussed herein may comprise various configurations, such as GSM, CDMA, time division multiple access (TDMA), UMTS, second generation (2G), third generation (3G), high speed packet access (HSPA), time division-synchronous code division multiple access (TD-SCDMA), time division-code division multiple access (TD-CDMA), etc. The makeup and functionality of these and other mobile core networks is well-known in the art and is thus not described in great detail herein.
A mobile core network may be formed using any of various wireless communication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other networks. The terms “network” and “system” are often used interchangeably. A CDMA network may implement a radio technology, such as Universal Terrestrial Radio Access (UTRA), Telecommunications Industry Association's (TIA's) CDMA2000®, and the like. The UTRA technology includes Wideband CDMA (WCDMA) and other variants of CDMA. The CDMA2000® technology includes the IS-2000, IS-95 and IS-856 standards from the Electronics Industry Alliance (EIA) and TIA. A TDMA network may implement a radio technology, such as Global System for Mobile Communications (GSM). An OFDMA network may implement a radio technology, such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, and the like. The UTRA and E-UTRA technologies are part of Universal Mobile Telecommunication System (UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are newer releases of the UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization called the “3rd Generation Partnership Project” (3GPP). CDMA2000® and UMB are described in documents from an organization called the “3rd Generation Partnership Project 2” (3GPP2).
In the traditional cellular telephone network (or “mobile core” described above), the coverage of the macrocell base stations is not uniform. For example, individual buildings may have weak signals indoors. Accordingly, more recently the addition of wireless router femtocell base stations has evolved. A femtocell is sometimes referred to as a “home base station”, “access point base station”, “3G access point”, “small cellular base station” and “personal 2G-3G base station”. In general, a femtocell is a small cellular base station designed for use in residential or small business environments. It connects to the service provider's network via broadband (such as DSL or cable) and typically supports 2 to 5 wireless communication devices (e.g., telephones) in a residential setting. A femtocell allows service providers to extend service coverage within a targeted small geographic location, such as within a user's home or business—especially where access would otherwise be limited or unavailable—without the need for expensive cellular towers.
A femtocell may thus be deployed directly within the wireless subscriber's premises, such as at a home or office. With a conventional femtocell, the wireless communication device (e.g., cellular telephone) accesses the femtocell base station through traditional licensed spectrum, and the handset connects to the femtocell via a radio link that implements traditional mobile network standards. The power levels between the femtocell and the attached mobile user equipment (UE) are generally much lower than the power levels between a macrocellular base transceiver station (BTS) and UE, since the limited range of the femtocell is intended to cover a much smaller geographical area (e.g., the subscriber's premises).
In most femtocell designs, connectivity to the mobile network or public switched telephone network (PSTN) is provided through an Internet connection, and calls are connected through Voice over Internet Protocol (VoIP) technologies. Other techniques are possible, such as utilizing a Bluetooth connection between the mobile user equipment (e.g., handset) and a personal computer or peripheral, as implemented in the Glide product from British Telecom (BT). In general, mobile operators are currently focusing on the UMA and femtocell approaches.
Generally, the femtocell incorporates the functionality of a typical base station but extends it to allow a simpler, self-contained deployment. For example, a UMTS femtocell may be implemented containing a Node B, RNC and GSN with Ethernet for backhaul. Although much attention is focused in the industry on UMTS, the femtocell concept is applicable to all standards, including GSM, CDMA2000, TD-SCDMA and WiMAX solutions.
For the mobile user, the attractions of a femtocell are improvements to both coverage and capacity, especially indoors. Femtocells offer an alternative way to deliver the benefits of Fixed Mobile Convergence (FMC). The distinction is that most FMC architectures require a new (dual-mode) handset which works with existing home/enterprise Wi-Fi access points, while a femtocell-based deployment will work with existing handsets with an installation of a new access point.
Currently, there are two broad femtocell architecture approaches within a mobile service provider's network: 1) all-IP (SIP/IMS) based approach, and 2) IP RAN based approach. The SIP/IMS based approach integrates the femtocell through a SIP or IMS based network. This approach leverages a SIP based (voice over IP) VoIP network for cost-effective delivery, while interworking with a cellular core to extend legacy circuit switched services. In this approach, the customer premise equipment (CPE) converts cellular signals to SIP and interfaces to a SIP-MSC inter-working function (IWF) which connects to the SIP (or IMS) network as well as the circuit-switched network.
The IP RAN based approach effectively considers a femtocell an extension into the operator RAN network and ties the femtocell into the circuit-switch core at the edge of the network. This typically involves transporting “Iub” messages over IP into a Radio Network Controller (RNC) or a modified RNC/concentrator. (The Iub is the interface used by an RNC to control multiple Node B's in a UMTS network.)